Jim Boylen's tenure as head coach of the Chicago Bulls is off to a rocky start, and after a week packed with grueling practices, extreme substitution patterns, and embarrassing losses, Sunday was the boiling point for many players on the team.

Some even contacted the National Basketball Players Association after Boylen scheduled a practice on Sunday following a back-to-back on Friday and Saturday - an unusual practice in the NBA - league sources told Yahoo Sports' Vincent Goodwill and Chris Haynes.

That practice did not occur, as players considered not showing up before ultimately holding a meeting to air grievances with coaches and the front office.

Another major sticking point with players was Boylen's decision to initiate a pair of five-man substitutions during Saturday's 56-point loss to the Boston Celtics. Bulls players reportedly felt humiliated by the gesture and then rebuffed Boylen's attempt to draw parallels with legendary San Antonio Spurs coach Gregg Popovich.